Spring biased diaphragm device



March 20, 1956 NEW (ONSTUCTMN H. L.. HARTZELL ET AL SPRING BIASED DIAPHRAGM DEVICE Filed 001.. 14, 1950 /NVENTOS HERMAN L. Hnerzfu. mm Jou W. DYER 2,738,808 Patented Mar. 20, 1956 United States Patent' vOffice SPRING BIASED DIAPHRAGM DEVICE Herman L. Hartzell, Anderson, and `John WQDyer,

Pendleton, Ind., assignors to General Motors Corporation, Detroit, Mich., a corporation vof Delaware Application October 14, 1950, Serial No. 190,115 i 1 Claim. (Cl. 137-790) This invention relates to tiuid pressure responsive devices such as devices operated by the suction of an internal combustion engineto effect a control of a circuit breaker lever carrying `plate of the ignition timer of the engine. In the control of ignition timing in accordance with engine suction, it is desirable that the movement imparted to the circuit breaker lever plate be substantially in direct pro portion to the amount of engine suction throughout the range of movement of the plate. Suction devices used heretofore provide for connection with the engine intake of a suction chamber enclosed by a metal case and a circular diaphragm, the periphery of which is clamped by the case and the central portion of which is connected with a member for transmitting motion to the circuit breaker plate. Movement ofthe diaphragm in response to engine suction is opposed by a helical coil spring which offers resistance in proportion to its deection. The sideof the diaphragm external of the suction chamber is exposed to atmospheric pressure. It is desirable that the force corresponding to the difference between atmospheric pressure on one side of the diaphragm and partial vacuum on the other side be opposed by the spring alone so that none of this force be consumed by stretching the diaphragm. To accomplish this it has been the practice to provide suticient diaphragm material between its peripheral and central portions to eliminate stretching of the diaphragm during its range of movement. In devices used heretofore it has been found that the usable force resulting from the effective pressure differential upon the diaphragm diminishes as the diaphragm approaches the end of its travels in which the spring is additionally compressed with the result that the diaphragm movement is not in direct pros. portion to engine suction throughout its range ofmovement. l

An object of the present invention is to provide a suction device in which diaphragm movement will be substantially in direct proportion to engine suction throughout the range of movement of the diaphragm. To accomplish this object the present invention provides a diaphragm ap' proaching a piston-like construction and having at the same time such flexibility that the diaphragm is not required to be stretched during its range of movement.

Further objects and advantages of the present invention will be apparent from the following description, reference being had to the accompanying drawings wherein a preferred embodiment of the present invention is clearly shown.

In the drawings:

Figs. 1 and 2 are longitudinal sectional views showing, in a device used heretofore, the position of the diaphragm at the ends of its range of movement.

Figs. 3 and 4 are longitudinal sectional views of a suction device embodying the present invention showing an improved diaphragm in two positions.

Fig. 5 is a side view of an assembly of diaphragm and other parts used in the device shown in Figs. 3 and 4.

Fig. 6 is a sectional view on line 6 6 of Fig. 5.

Fig. 7 is a fragmentary view on line 7-7 of either Fig. 2 or Fig. 4.

Referring to Figs. 1 and 2 showing an old construction device comprising a case including shell members 10 and 12 having flanges 11 and 13 respectively between which the periphery of a diaphragm 15 is gripped by deforming the flange 11 around the flange 13 as indicated at 11a. A suctionchamber 16 is provided between shell 10 and diaphragm 15 and it is connectible with the engine intake by attaching a pipe to a bushing 17 threaded into a tube 18 attached to shell 10. Shell 12 is opened to atmosphere through an opening 19 which receives a bar 20 which together with a cup washer `21 is secured by a rivet 22 to the central portion of the diaphragm. A helical coil spring 23 is located between the plug 17`and the washer 21. The spring 23 is initially compressed so that it urges shoulders 24 of the bar 20 against a mounting bracket 25 used to attach the diaphragm housing to a device to be controlled by engine suction such as an ignition timer. The bar 20 provides a connection between the diaphragm and a rotatable circuit breaker lever carrying plate of the timer. Bracket 25 (Fig. 7) provides a triangular opening 26 through which the widest portion of bar 20 can be passed as indicated at 20' (Fig. 7) before the'diaphragm housing is attached to the bracket 25. When these parts are properly assembled the narrower portion 20a of bar 20'wil1 be located in the narrower portion of the opening 26. Therefore left movement of the diaphragm as engine suction increases will be stopped when shoulder 27 of bar 20 engages bracket 25 as shown in Fig. 2.

In order that the diaphragm material between its central and peripheral portions will be such that the suction upon the diaphragm will not require it to be stretched itis the practice to lightly crimp flange 11 of shell 10 around flange 13 of., 4shell `12. Then suction is applied to cause the diaphragm to move left to the limit of its travel as shown in Fig. 2 to tightly crimp flange 11 as shown at p 13. As the diaphragm moves to the position shown in Pig. 2 by applied suction before final crimping of shell flange 11, the diaphragm pulls away from these anges. Consequently, after the final crimping of flange 11 none of the suction eect is used in stretching the diaphragm.

As engine suction increases to overcome spring 23 and to cause diaphragm 15 to move to its extreme left position as shown in Fig. 2, the effect of suction substantially decreases. In Fig. 2 the arrows 15A represent the direction of applied atmospheric pressure. Some of these forces are not parallel to the axis of the spring hence the force components parallel to the spring are less than they would have been if the forces had been parallel to the spring. Furthermore, the diaphragm is drawn into contact at 15B with shell 10. As the diaphragm approaches shell 10 the eect in area of the diaphragm substantially decreases with the 'result that movement of member 20 in response to increase of engine suction does not remain in direct proportion to engine suction but diminishes in proportion to increase of engine suction.

The device embodying the present invention provides a diaphragm 35 of fabric treated with a suitable plastic material such as neoprene which is molded into the form shown in Fig. 6. A rivet 42 secures to the diaphragm a motion transmitting member 40 shaped like member 20, shown in Fig. l, and a washer or discs 41 of relatively large diameter having a peripheral flange 41A to prevent cutting the diaphragm. The washer is provided with a circular row of tangs or fingers 41B providing a seat for a helical coil spring 43 which is located between the washer 41 and a plug 37. The plug is threaded into a sleeve 38 attached to a housing shell 30 having a flange 31 which together with the periphery of the diaphragm is forced against a flange 34 of a housing shell 32 by crimping flange 34 about flange 31 as indicated at 33. 'I'his assembly of parts is assembled with amounting bracket 45 provided with an aperture 26 like that shown in Fig. 7 for receiving the n member 40. In the mannerdescribed with reference to Fig. 3, the bracket 45 provides a stop limiting movement of member 140 iin both directions. The opening ZGinibrac'ket 4S and the opening 39 in shell 32 provides for Venti'n'gvthe space to the right ofthe diaphragm 35.

As engine `suction increases to overcome :spring y43 to cause movement of 'the diaphragm-35 toward the-extreme left position shown in Fig. 4 the forces representing the difference between atmospheric pressure lon the right of the diaphragm and sub-atmospheric pressure to the left of the diaphragm are forces `which are nearly all parallel to the axis fof spring 43 as :indicated by arrows 35A. The extent to which the differential force Ais :not 'gparallel to spring axis Aas represented by :arrows 35h is y.relatively-small in proportion t0 'the total force. Therefore for allpiactical purposes the diaphragm 35 operates llike la piston in response to engine suction so that movement of 'member 40 to the left is substantially indirect proportion @to increase of 4engine suction. The washer -41 of relatively large diameter maintains the major :portion of the diaphragm in a plane atvright angles to theaxis-of spring-43. The portion included between the clamp peripherally fof the diaphragm'and-'the'at centralportionthereof provides exibility sufficient ffor movementof the diaphragm without stretching. Therefore there lis substantially ino force consumed in changing the =shape'o'f the diaphragm of this flexible portion .from that .shown 'in lFig. 3 fto .that shown in Fig. 4. Therefore the diaphragm ofthe present device performs l.a function approaching that of a friotioriless Apiston moving into opposition to a helical coil :springas pressure diierential increases.

While the embodimentof vthe present invention as herein disclosed, constitutes 'a preferred '=form, it :is rto be -understood that other forms :might 4be adopted.

What is olaimedfas as follows: v

A device for effecting mechanical 'movement -in accordance with a iluid pressure differential, the combination comprising; a case,'a flexible-diaphragm rsealingly attached along vthe peripheral edge to said case and dividing said case into a first and second chamber and forming a movable wall therebetween, said rst chamber having one pressure therein and the second chamber being connected with a source of a variable lower pressure, said diaphragm being adapted to move between two extreme positions in response to variations of the pressure within said second chamber, a peripheral annular fold adjacent the peripheral edge of said 'diaphragm when said edge is attached to said case, a lever attached to the rst chamber side of said diaphragm adapted to be moved thereby between limits as defined `by stops 'associated with said lever when said stops engage portions of the case, a disc attached to said diaphragm on the second chamber side having a rounded edge adapted to engage a portion only of said diaphragm and terminating short of said fold, a spring disposed between a wall of the second chamber and said disc for opposing the movement of said diaphragm in response to variations lin said pressure, a plurality of centrally disposed -fingers integrally formed on said disc for maintaining said spring in position with respect thereto and within said chamber, said diaphragm being adapted to be vmoved to substantially bottom in said rst'chamber in one ,position -by saidrspring when the pressures in said chambers are substantially equal and move to the other extreme position :in response -to said pressure variation while said fold in the diaphragm diminishes in size and is constantly maintained.

References Cited in the file of this patent 5Ul'SITl-:D STATES PATENTS 1,790,206 Farmer Jan. 27, l1931 1,999,285 Davis Apr. 30, 1935 2,380,983 Mock Aug. 7, '1945 '2,444,163 Kocmich June 29, `1948 2,447,261 Mock Aug. 17, `1948 '2,658,526 'Porter Nov. 10, 1953 FOREIGN PATENTS 503,463 Great Britain Apr. 6, 1939 

